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      05-22-2020, 09:12 AM   #1
belcom
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short term tire/wheel dilemma

I had inherited the wheels from previous owner, RTX Envy 18x8 all around with Conti SSR runflats which still have quite a bit of tread. He used 225/45 front and 245/40 rear. Stock staggered setup calls for 255 rear. I was not too happy to learn that but then understood why that happened. Can't really put 255 tire on 8in wheel.

Now the ride with these tires and these sizes is FAR from optimal. I know that Z4 has a tendency to wonder and follow grooves and as it stand now that's what the car is doing to a point of being quite bad. Plus I dunno whats going on with these runflats but they vibe like crazy too. Probably from standing for long periods of time and they flat spotted but I have not driven the car enough yet to actually try to straighten them out. And not even sure if they will eventually work out these flat spots.

Suspension refresh coming up very soon and hoping that will take care of some of the issues with wondering but ultimately I need to look at tires as well.

I do like the style of these wheels, but they're cast, not light, not the size I need/want and tires are just the regular crappy runflats. This season getting a new set of wheels I want is not on the map due to budget but I need to be able to enjoy the car for the season and maybe do a little bit of light track driving with it.

Thinking of going with a 245/40/18 square setup and get a set of used but good condition non-runflat for now while next year I'll be getting some proper wheels and tires that will permanently stay.

Here's my question, if you ran both staggered and square setups on your Z4 what kind of experience, feel, difference did you see?

Also, any advice on how to work out the flat spotting? I read somewhere to put as much air as the tire allows and drive it for 100-150kms. On my other car I have brand new eagle F1s and they flat spot too if I let the car sit for at least a week. However, after driving for 10-15 minutes it becomes smooth and good to go. The run flats on Z4 are still vibrating after even 30 minutes of driving around I'd keep them for at least this season but vibrating cars is a pet peeve of mine. I hate it!! So something needs to be done very soon.
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      05-22-2020, 09:17 PM   #2
CTMP4me
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Quote:
Originally Posted by belcom View Post
Here's my question, if you ran both staggered and square setups on your Z4 what kind of experience, feel, difference did you see?

Also, any advice on how to work out the flat spotting? I read somewhere to put as much air as the tire allows and drive it for 100-150kms.
Square setup on non-runflat tires is the ticket, will be nice even running 245s all around. Less understeer, more front end grip, better turn-in "bite", all good things, plus ability to rotate wheels front to back and keep wear even. As part of the switch, check your alignment as well and dial in as much as front camber and caster as stock suspension setup allows.

I left my M coupe sitting all winter on its street Michelin PS4S, no special overinflation or anything, and if there was any flat spotting, I didn't notice it. YMMV with runflats though.
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      05-23-2020, 07:03 AM   #3
belcom
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Quote:
Originally Posted by CTMP4me View Post
Quote:
Originally Posted by belcom View Post
Here's my question, if you ran both staggered and square setups on your Z4 what kind of experience, feel, difference did you see?

Also, any advice on how to work out the flat spotting? I read somewhere to put as much air as the tire allows and drive it for 100-150kms.
Square setup on non-runflat tires is the ticket, will be nice even running 245s all around. Less understeer, more front end grip, better turn-in "bite", all good things, plus ability to rotate wheels front to back and keep wear even. As part of the switch, check your alignment as well and dial in as much as front camber and caster as stock suspension setup allows.

I left my M coupe sitting all winter on its street Michelin PS4S, no special overinflation or anything, and if there was any flat spotting, I didn't notice it. YMMV with runflats though.
I had never experienced issues with any Michelin tire as well and went through many different kinds over years including a set of PSS. Michelins are my tires of choice.

Thanks for your input on square setup. I think that's what I will end up doing this season. Will try to locate a decent set of Michelins.

And alignment is definitely going to be done as soon as suspension is in. I will talk to them about camber.
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